Method of coating substances



*nuenis. ooornn ANDMENAHEMMERLUB-SOBEL; or; CLEVELAND, OHIO, .nssrenons,

Nb arming;

Patented Sept. 26, 1932 FF'ETF S- 1 TO K-EMET- LABORATORIES, INC.,. ACQRPQR A'IION"OF;'NEW YORK METHOD or coA'rINe suBsrAnoEs i l -Tl1isinvention relates to a method of coat ing substances With metal ormetals of the alkali or alkaline-earth groupsyand With the oxids ofsuch'me'tals.

to a method of making such elements, it Will hereafter be described inthat connection, by Way ot suitable example.

Gathodesotthedull-emitter or Wehnelt typeerdi-n arily consist of aplatinum or other metallic core, -usually in the formof a W1-I6'1 orribbon, which has been coated with oxid of: some metal or metals, suchas'fbar um, strontium, or the hlze. Several methodslha've "fheretoforebeen employed in the production ofisuch cathodes. One of theolder processes is todip' the-Wire to be coated into a solution ot thenitrate of the-desired metal ormetals,

andthenfl decompose the nitrate by heating =in inert atmosphereinorderto' obtain the ox id. Ibis-ordinarily necessary to apply aconsiderable number of successive coats of oxid; in this .manner if auniform 1 electron emission is :to be obtained frcm the finished"element-1n another method of producing an oxid coating the-heated Wireis brought into contact With solid p'arafiine in which is suspendedaco'nsiderable amount of'barimn onstrontium carbonate, orithe like. Thecar- -bonates being decomposed, an 'ox1d1coat1ng remains. In thls case,also, a large number of successive coatings arerequired; Still a thirdmethod is to paint or coat the Wire With a solution of bariumaZide,.-andthen apply heat in order'ito. decompose thecompoundto metallic barium,Which readily oxidizes.

Each of these methods is open to a number of objectives, and presentscertain definite disadvantages. In the first two methods there F-is notonly the already mentioned necessity for applying a large number ofsuccessive coatings of oxid if a stable or uniform electron emission isdesired, Which is troublesome and expensive in itself, but there is thefur- 'ther difliculty that considerable quantities of Application fi ledSeptember 20,1327. Serial at. 220,532.

gas are apt -to-be occludedduring the'c'oating process. It is extremelydifiicult', or impos;

PATENT one f sible, completely to remove this occluded gas C during thesubsequent evacuationof the-tube,

and this may account, to-some extent, for-thefrequente'rra'tic behaviorof cathodes made in this Way. Moreover, it is diflicult to make thecoatings of uniform thickness ,and hot: spots and consequent burning outof the filament frequently occur. -With' regard to the third process,barium az ideis a highly explosive; compound; its preparation is con Irespondingly 'diilicult, and" the process is so dangerous as to behighly unsatisfactory.

Our invention provides a means for applying metallic'oroxid coatings-tosubstances I ofany desired character." The methodis substantially freefrom the foregoing difii culties and objections; and results in-aimoreuniform and adherent coating than has been (so far as We areraware)hitherto obtainable.

According to our invention We dissolve an alkali or alkaline-earthmetal,'or a salt or oxid off'such ametal, in anorganici'solvent, either'by direct solution in the caseof a metal compound; or by converting themetal to anorganic compound by' means of the solvent,

and solution'of the resulting compound, inthe caseiot a metal. Wethenapply the resulting solution to'the substance, :for example a cathodeelementior filament-,which isto be coated. The solvent isflthenevaporated, by-

exposure to the air or otherwise, when a uniform v and adherent 1coating of the dissolved: compound remains- In the event that a metal,or a. saltrnot'an oxid, Was employed,

the coatin'gmay be readily converted to oxid by. furtherv exposure tothe air, or by heating in airor other oxidizing atmosphere itnecessaryyu I Particular examples of methods of"carry-- ing-outourinvention are as follows l i c 1. Barium iodide is'dissolved in ethylalcoholto form asaturatedsolution? This solution isi'applied to;afil'ament element b'y dip ping, brushing, l-or oth'erWise.'.- The"element is then exposed-"to the air until the alcohol evaporates; The"element isithen heated, preferably by means of 1ts own 'resistance'to'an I electric current, 111 a'an oxldizmg atmos-fl phere in order toconvert the barium iodide into emissive barium oxid. The resultingcoating is firm, uniform, and adherent.

2. Barium oxid is dissolved. in ethyl alcohol and applied toa filamentelement in the same manner. Heating in an oxidizing atmosphere isgenerally unnecessary in this case.

3. Barium metal is treated with an excess ofethyl alcohol to form bariumethylate, which is dissolved in the excess alcohol to form a solution ofbariumethylate; This solution is applied as before, andthe coating ofbarium ethylate which remains afterevaporation of the solvent isdecomposed by heating to form the desired oxid coating,

.4; Barium metal-is dissolved-in an excess of acetone toform a solutioninacetone of barium enol-acetonate, which is employed as -inExample 3above.

It must be understood that the foregoing examples are merelyillustrative of our in ventlon, which, is, of course, not limltedthereto.

Throughout the foregoing examples we have referred to the metal barium,or its salts or oxids,for the sake of uniformity. Calcium, strontium, orother metals of the alkaline-earth group, their salts or oxids, mayreplace, or be used in conjunction with, barium, or alternatecoatingsofdifierent compositions, may be employed. The sameapplies,also, to alkali metals such as'sodium, potassium, etc., or theircompounds. Vie

gfrequently employ solutions; containing-several of these metals, orapply alternate coat ings derived from different solutions.

According to our invention, also, when two or'moreseparate organicsolvents are .miscible, we may employ a suitable mixture of solvent-storeplace a single one, and such a mixture is included by the term organicsolvent? or the like as herein employed. j

With regard to the substance whichis to receive. a metallic or oxidcoating, we may employ 'a'metal in the form of a wire, filament, ribbon,small tube or rod, plate,'orthe like. chromium alloys, are-good,examplesof metals which'act satisfactorily inzreceiving and retainingthe coating. Even more refractory metals, such as tungsten, molybdenum,tantalum, platinum, etc., are also suitable. Our invention, however isnotc'onfinedto coating metallic substances. In some cases we wish.

to apply a metal or oxidcoating to a nonmetallic substance. such asporcelain, silica, and so forth; There are certain types of cathodes(used in the so-called heater tubes).

fin which the. emitting surface isnot identical with the heatingelement, but comprise a tube or. small cylinder, etc., which is heatedby means of a separate filamentor heater arranged within it. Ourinvention is equally applicable to coating ,such emitting elements Wehave found that nickel, or nickel line-earth oxid material to form anelectronemitting cathode element, which comprises treatingalkalineearthmetal with an organic solvent to'form 'an'organic compound, dissolvingsaid compound in excess ofsaid solvent," applying the resulting solutionto the substance to be coated, and converting the resulting coating tooxid.

2. Process of coating a non-metallic'refractory element with.alkaline-earth oxid v material to form an electron-emitting cathodeelement, which comprises treating alka- 1 line-earth metal with anexcess of organic solvent to form a solution, applying the solution tothe non-metallic refractory element to be coated and converting theapplied solution to anoxid coating. n

3. Process of coating a metallicelement with barium oxid material toform an electron-emitting cathode element, which comprises treatingbarium metal with an excess of ethyl alcohol to form a solution,applying :1

the solution to themetal to be'coated and converting the appliedsolution toian oxid coating; V V a 4:. Process of coating'a metallicelement with barium oxidmaterial to form .an'electron-emitting cathodeelement, which com-- prises treating barium metalwith an excess. ofacetone to form a solution, applying the solution to the metal to becoated and converting the applied solutionto an oxidcoat- ,5. Processofcoating a metallic element.

with barium oxid material to form an elec-.-. tron-emitting cathodeelement, which comprises treating barium metal with an excess of asaturated aliphatic oxygen-containing organicsolventto' form asolution,apply-v 1 ing the solution to the metal to be coated and converting theapplied solution to an :oxid coating.

In testlmony whereof, we aflix our signature. t

HUGH S. COOPER. MENAHEM MERLUB-SOBEL.

